CAMBRIDGE, Mass./WASHINGTON (Reuters) - Delivering her first speech as the top U.S. environmental steward, Gina McCarthy on Tuesday pre-empted a frequent mantra of critics of the Environmental Protection Agency - that the agency's regulations disrupt the economy and cost jobs.

The benefits derived from rules to address climate change and protect the environment far outweigh their costs, said McCarthy, who was confirmed by the U.S. Senate on July 18 as EPA administrator.

"Can we stop talking about environmental regulations killing jobs, please?" McCarthy said in a speech at Harvard Law School in Cambridge, Massachusetts.

The EPA, often a lightning rod for Republican opposition in Congress, is working to develop "a new mindset about how climate change and environmental protection fits within our national and global economic agenda," McCarthy said.

Embracing the need to cut carbon emissions should be seen not as a threat but as a "way to spark business innovation," she said.

The federal Clean Air Act, the basis of the EPA's powers to set rules, has produced $30 in benefits for every dollar spent in its name, she added.

McCarthy was confirmed after a months-long process that at one point involved a Republican boycott of a committee vote and required her to answer more than 1,000 questions posted by senators about the EPA's rulemaking processes and transparency.

The speech, just a few miles from her hometown of Boston, marked the start of a nationwide tour to talk about why acting on climate change is necessary and to dispel common criticisms.

McCarthy, along with Energy Secretary Ernest Moniz and Secretary of the Interior Sally Jewell, is making public appearances to help President Barack Obama roll out the Climate Action Plan he announced in June.

At the heart of Obama's plan will be new EPA regulations that will target carbon emissions from existing power plants, which account for more than one-third of U.S. greenhouse gases and in many cases are fired by coal.

McCarthy said the agency will try to replicate the success it had with the U.S. automotive industry, with which it collaborated to craft new fuel efficiency standards.

"This is a game plan for other sectors to follow on how we can reduce emissions, strengthen energy security and develop new economic benefits for consumers and businesses," McCarthy said.

In addition to close collaboration with industry, McCarthy said she will look to states and local governments that have piloted emission reduction policies and blueprints without waiting for Washington. She said the EPA would not be a leader, but a follower of states' programs to curb emissions, relying on the work they've already put into force.

'HONEST COMMENTER' ON KEYSTONE

McCarthy also addressed one of the most controversial environmental and energy issues facing the Obama administration - the proposed Keystone Pipeline project.

Responding to a question about the climate impact of the 830,000 barrel per day pipeline, McCarthy first jokingly pretended to walk away from the podium before responding.

"In all seriousness, I think the best that EPA can do is to be an honest commenter on the environmental impact statement, which we've done our best to do and which we'll continue to do," she said.

An assessment of the project by the EPA released in March raised concerns about the analysis done by the State Department, which found there would be no significant effect on greenhouse gas emissions.

McCarthy said the Obama administration was examining all aspects of the pipeline proposal.

"It is not supposed to be easy," she said. "It is supposed to be hard, it is supposed to be all interests coming together and screaming at the top of their lungs like three crazy children."

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